This invention relates to nuclear reactors and nuclear fuel elements for use in nuclear reactors cooled by light or heavy water.
The fuel elements for these reactors commonly comprise nuclear fuel rods supported in parallel spaced apart positions in suitably proportioned clusters or bundles so that within the nuclear reactor core, coolant passed over the fuel rods in a direction parallel to their surfaces becomes heated. Thereafter the heated coolant is employed in a heat utilisation plant for example a heat exchanger or a steam turbine.
Various proposals have been made for providing an auxiliary means of cooling the nuclear fuel clusters by means of one or more spray cooling tubes which, connected to their own supply of coolant extend within the cluster parallel with the rods, and from holes in the side walls of these tubes, coolant water may be sprayed laterally into the cluster against the rods. The flow of main coolant may thus be supplemented by the auxiliary coolant or replaced by the auxiliary coolant in some circumstances.
A difficulty in these arrangements is that only those fuel rods close to a spray cooling tube have a line of sight to it and can readily be reached by the auxiliary coolant.